Commit a474e52c authored by Paul Cercueil's avatar Paul Cercueil Committed by Ulf Hansson
Browse files

mmc: jz4740: Support using a bi-directional DMA channel 



Since the MMC/SD controller in Ingenic SoCs work in half-duplex, it is
possible to use one single DMA channel for both TX and RX operations,
instead of using separate channels.

As some older Ingenic SoCs offer only a handful of DMA channels,
supporting bi-directional channels allow more hardware to use the
channels that would otherwise be used for the MMC/SD operation.

Signed-off-by: default avatarPaul Cercueil <paul@crapouillou.net>
Link: https://lore.kernel.org/r/20211220190840.108061-3-paul@crapouillou.net


Signed-off-by: default avatarUlf Hansson <ulf.hansson@linaro.org>
parent 34ce2930

drivers/mmc/host/jz4740_mmc.c

+17 −2
Original line number Diff line number Diff line
@@ -217,11 +217,23 @@ static void jz4740_mmc_release_dma_channels(struct jz4740_mmc_host *host) 
		return;



	dma_release_channel(host->dma_tx);

	if (host->dma_rx)

		dma_release_channel(host->dma_rx);

}



static int jz4740_mmc_acquire_dma_channels(struct jz4740_mmc_host *host)

{

	struct device *dev = mmc_dev(host->mmc);



	host->dma_tx = dma_request_chan(dev, "tx-rx");

	if (!IS_ERR(host->dma_tx))

		return 0;



	if (PTR_ERR(host->dma_tx) != -ENODEV) {

		dev_err(dev, "Failed to get dma tx-rx channel\n");

		return PTR_ERR(host->dma_tx);

	}



	host->dma_tx = dma_request_chan(mmc_dev(host->mmc), "tx");

	if (IS_ERR(host->dma_tx)) {

		dev_err(mmc_dev(host->mmc), "Failed to get dma_tx channel\n");
@@ -241,7 +253,10 @@ static int jz4740_mmc_acquire_dma_channels(struct jz4740_mmc_host *host) 
static inline struct dma_chan *jz4740_mmc_get_dma_chan(struct jz4740_mmc_host *host,

						       struct mmc_data *data)

{

	return (data->flags & MMC_DATA_READ) ? host->dma_rx : host->dma_tx;

	if ((data->flags & MMC_DATA_READ) && host->dma_rx)

		return host->dma_rx;

	else

		return host->dma_tx;

}



static void jz4740_mmc_dma_unmap(struct jz4740_mmc_host *host,